1. Field of the Invention
This invention relates to new and improved methods and apparatus for opposing deformity, displacement, and expulsion of the ocular tissues during eye surgery. The method and apparatus are for use during eye surgical procedures in which an incision is made into an internal compartment of an eye. Such eye surgical procedures include various types of corneal, cataract, vitreous, retinal, and glaucoma surgery. The method and apparatus are also for use during eye surgical procedures to repair an eye already cut open by traumatic injury. The method and apparatus also provide a means of regulating pressure within the eye during surgery. The method and apparatus also provide a means of filtering and humidifying the air in the vicinity of the open incision. The particular surgical case must be evaluated to determine whether or not the use of the method and apparatus is appropriate.
2. Description of the Prior Art
The state of the art of methods and apparatus for performing eye surgery may be ascertained in large measure by reference to U.S. Pat. Nos. 3,186,308; 3,612,468; 3,868,171; 4,014,342; 4,108,182; 4,184,491; 4,019,514; 4,157,718; 4,041,947; 4,168,707; 4,184,510; 4,184,492; 4,180,074; and 3,572,319; "Vitreous Microsurgery" by Steve Charles (Williams & Wilkins, Baltimore, 1981); "Surgery of the Eye" by E. D. Dorrell (Blackwell Scientific Publications, London, 1978); "Cataract Surgery and Its Complications" by Norman S. Jaffe (C. V. Mosby Company, St. Louis, 1981); "An Atlas of Ophthalmic Surgery" by John Harry King, Jr. and Joseph A. C. Wadsworth (J. B. Lippincott Company, Philadelphia, 1981); "Microsurgery of the Anterior Segment of the Eye" by Richard C. Troutman (C. V. Mosby Company, St. Louis, Volume I, 1974, Volume II, 1977); and Weck Optical Product Bulletins, "016 XY Translation Arm (1981)" and "004 XY Translation Table" (Edward Weck & Company, Inc., Box 12600, Research Triangle Park, N.C. 27709), the disclosures of which are incorporated herein.
Many surgical procedures are employed to restore, preserve, or improve vision. Some of these, including cataract surgery and penetrating keratoplasty (corneal transplantation), require that a surgical incision be made into the tissues and compartments of the eye. Before such an incision has been made, an eye with a normal intraocular pressure of about 15 mm Hg. above atmospheric maintains a steady resistance to deforming forces. Even an eye with an intraocular pressure measuring zero relative to atmospheric pressure can, before an incision is made into the intraocular compartments, offer considerable resistance to transiently applied forces by responding with a transient rise in intraocular pressure. However, an eye with a cut connecting its internal compartments with the operating room space at ambient atmospheric pressure has lost most of its ability to resist deformation because the ocular tissues can flow out through the opening, unimpeded, as a deforming force is applied. Various deforming forces bear upon the eye at various times during surgery. Thus, when a surgical incision is made, there is a tendency for the eyeball to assume a distorted shape and for fluid and tissue to be displaced towards the incision and to be expelled from the eyeball through the incision. The deformation results from the action of gravity on the tissues and fluids of the eye, from the contraction of the normally stretched elastic fibers of the ocular wall, from the pull of muscles fastened to the outside of the eye, and from the effect of compressed orbital structure. The deformation can also result from the pressure of surgical instruments laid on the eye or the orbit. Furthermore, when the surgical incision is made, the pressure within the eye, which, in a normal eye, is about 15 mm Hg. above atmospheric, falls towards atmospheric pressure, i.e., towards the ambient pressure in the operating room. This fall of the intraocular pressure favors seepage or "transudation" of fluid from the lumens of capillaries in the structures of the eye, through the capillary walls, and into the tissues and compartments of the eye. The fall in intraocular pressure also favors the occurrence of intraocular hemorrhage due to the failure of support for weak points in the walls of blood vessels of the eye which then rupture. Both transudation and hemorrhage contribute to internal deformation and loss of tissue or fluid through the incision. If a choroidal hemorrhage of sufficient magnitude occurs, the entire contents of the eye, including the retina, can be rapidly and unavoidably expelled, resulting in loss of the eye. In general, the greater the ocular deformity taking place during surgery, the greater the ocular damage, the greater the difficulties encountered by the surgeon, and the poorer the results of the surgery.
Various methods of dealing with the problems of intraocular hypotension, anterior (forward) displacement of the contents of the eye towards and through the incision, and ocular deformity during surgery have been described.
One such method attempts to maintain the intraocular pressure above atmospheric pressure by forcing fluid into the eye through a needle or cannula. As a result of the maintenance of this pressure differential between the inside of the eye and the air in the operating room while the eye is cut open, there is a tendency for fluid or tissue to be pushed out through surgical incisions, be they for the insertion of microsurgical instruments or for the infusion cannula itself. The size and position of the various incisions as well as the position of the infusion cannula influence to a considerable degree the tendency for fluid or tissue to be extruded. Since it might harm the eye if tissue prolapses, if excessive leakage prevents pressure maintenance, if excessive leakage requires excessively high infusion and intraocular flow rates, or if excessive leakage obscures the surgeon's view, the incisions must be kept small, plugged, or blocked. Even with small incisions, the possibility that tissue will prolapse exists, especially during insertion and removal of an instrument.
In situations where a large incision is necessary, it is sometimes possible to reduce the blood pressure of the patient so as to reduce the risk of expulsive hemorrhage or significant transudation. However, manipulation of the blood pressure may compromise circulation of blood to the brain, the heart, the kidneys, as well as to the eye itself.
External mechanical support can be provided for the sclera, i.e., the ocular coat, at a finite number of points by attachment of a Flieringa ring, a scleral expander, or the like, around an anterior part of the eye. However, there is little support for the rearward portions of the eye because such external supports are sewed only to the exposed parts at the front of the eye. The effect of hemorrhage or transudate can still be to separate the choroid and the retina from the sclera because of failure of the external support to provide appositional force between these structures. Finally, such external skeletal supports may create undesirable stresses by supporting the sclera at the same time that the elastic choroid tends to collapse and fall away from it.
Other methods are also employed to reduce anterior displacement by producing a "soft eye", i.e., an eye which has an intraocular pressure lower than normal, before the incision is made. Such methods include compressive ocular massage, intravenous infusion of osmotic agents to draw water out of the body tissues, and the use of a needle to aspirate liquid vitreous. These measures reduce the ocular volume thus relieving compressive forces so that there will be less resulting anterior displacement of the ocular contents towards the incision when the incision is finally made. Paralyzing the ocular muscles with drugs such as intravenous curare is also employed. (Osmotic agents, liquid vitreous aspiration, and drugs such as curare are sometimes used after the incision is made.) These softening techniques have side effects and risks which are well known.
It is an object of this invention to provide the surgeon with a method and apparatus for maintaining desired anatomical relationships during the performance of surgery through an open incision of a size appropriate to the surgical task to be performed.